JPH08302241A - Powder paint - Google Patents

Abstract

(57) [Summary] [Objective] The object of the present invention is to use a powder coating having a small particle diameter that enables thinning of a coating film, and achieve improvement in working efficiency by thinning the coating film. The object is to obtain a powder coating which has both good rust resistance and weather resistance even when used for outdoor applications. A powder coating material containing at least a resin component composed of a binder resin and a curing agent, and having a volume average particle diameter of 5 to 20 μm, characterized by containing a silane coupling agent. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder coating suitable for thin film coating, and more particularly to a powder coating suitable for outdoor use.

[0002]

2. Description of the Related Art It is well known that powder coating materials have less volatile components and odors than solvent coating materials and are very useful in terms of pollution control and environmental regulations. The powder coatings that have hitherto been put on the market for general use have a volume average particle diameter of about 30 μm and have not been subjected to strict classification, so that the particle diameter distribution is very broad. In order to obtain uniformity of the coated surface after powder coating, it is essential to form a uniform powder adhesion layer, but for that purpose, an adhesion layer having a particle diameter of 2 to 3 times is required. Therefore, in the conventional powder coating material, a good coating surface could not be obtained unless the thickness of the coating film was 60 μm or more. On the other hand, as market needs, there is a demand for improvement of coating surface uniformity, improvement of work efficiency by thinning coating film, and total cost reduction.
A film thickness of about 0 μm is desired.

At present, powder coatings have been used not only for indoor coating but also for outdoor coating such as fences. Since a polyester resin or an acrylic resin alone is inferior in rust-prevention property, a conventional epoxy resin powder is added with a small amount of epoxy resin for the purpose of imparting rust-prevention property. But,
When epoxy resin is added, the deterioration of weather resistance becomes remarkable,
There is a problem that the weather resistance, which is an advantage of polyester resins and acrylic resins, is lost. In addition, the above 30-60
It has been confirmed that the thin film coating of μm tends to lower the rust preventive property as compared with the normal film thickness of 60 μm or more.

[0004]

The object of the present invention is to solve the above problems and to use a powder coating having a small particle diameter which enables the thinning of a coating film, and work by thinning the coating film. It is an object of the present invention to obtain a powder coating material that achieves improved efficiency and that has good rust prevention and weather resistance even when used outdoors.

[0005]

The present invention is a powder coating material containing at least a resin component composed of a binder resin and a curing agent, and having a volume average particle diameter of 5 to 20 μm, which comprises a silane coupling agent. It is a powder coating characterized by containing.

The present invention will be described in detail below. The powder coating material used in the present invention is composed of powder particles containing at least a resin component composed of a binder resin and a curing agent. As the binder resin, a resin having good weather resistance such as polyester resin, acrylic resin, silicon resin, or fluororesin is used. Further, as the curing agent, isocyanate, amine,
Examples thereof include polyamides, acid anhydrides, polysulfides, trifluoroboric acid, acid dihydrazides, imidazoles and the like.
Further, the powder particles include fillers such as barium sulfate, calcium carbonate, aluminum oxide and calcium silicate, leveling agents such as acrylic oligomer and silicone, coloring agents such as titanium oxide, chromium oxide, iron oxide and carbon black, You may add a foaming inhibitor etc. suitably.

The particle diameter of the powder coating composition of the present invention is 5 to 2 in terms of volume 50% measured by Coulter counter TAII type.
It must be in the range of 0 μm. Volume 50
Powder particles having a% diameter of less than 5 μm have a large inter-particle force due to van der Waals forces and the like, and are apt to agglomerate, which deteriorates the fluidity of the powder and is not practical as a powder coating material. Further, if it is attempted to manufacture such powder particles having a small particle diameter by a general melt-kneading and pulverizing and classifying method, a large amount of energy is required in the pulverizing and classifying step, so that the manufacturing cost becomes considerably high. On the other hand, if the volume 50% diameter exceeds 20 μm, a thin and uniform powder adhesion layer cannot be obtained on the coated surface, and therefore a good thin film cannot be obtained.

The powder coating material of the present invention is characterized by containing a silane coupling agent, whereby the adhesion between the coating material and the powder coating material such as stainless steel or aluminum is improved, and the rust preventive property is improved. To do.

The silane coupling agent has the general formula: X-Si (OR) ₃ where X is a functional group that reacts with an organic substance, and R is a hydrolyzable group. The adhesiveness between the organic substance and the inorganic substance is improved by the action of the two kinds of functional groups. Specifically, it is considered that a chemical covalent bond is generated between the organic substance (powder coating material) and the inorganic substance (object to be coated) as follows.

[0010]

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The silane coupling agent used in the present invention has an amino group, a methacryl group, an epoxy group, a vinyl group or the like as a functional group that reacts with an organic substance, and an alkoxy group as a functional group that reacts with a hydroxyl group on the inorganic surface. A general one having a group can be used. Specific examples of the silane coupling agent used in the present invention include the following commercially available products. However, it is not limited to these. γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, aminosilane, N-β-
(N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, methyltrimethoxysilane,
γ-methacryloxypropyltrimethoxysilane, γ-
Mercaptopropyltrimethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane.

The silane coupling agent used in the present invention is preferably added in the range of 0.5 to 2.5 parts by weight with respect to 100 parts by weight of the resin component. If it is less than 0.5 parts by weight, the adhesion to the article to be coated is not sufficiently improved. Also, 2.5
Since the effect of improving the adhesiveness is saturated in the vicinity of parts by weight, the effect depending on the added amount cannot be expected even if it is added over the range, and the cost of the material increases, which is not practical.

The powder coating material of the present invention can be obtained by dry-mixing the composition of the above-mentioned powder particles, hot-melt kneading, pulverizing and classifying. Alternatively, the above composition may be directly produced by various polymerization methods such as a spray drying method, a suspension polymerization method and an emulsion polymerization method.

The silane coupling agent used in the present invention may be added when the composition is dry-mixed, or may be attached to the surface thereof after being pulverized. In order to attach the silane coupling agent to the surface, the powder may be kept in a fluid state and the silane coupling agent diluted with the solvent may be sprayed.

Fine powder of hydrophobic silica or alumina may be added to the powder coating material of the present invention for the purpose of improving fluidity. The fine powder is adhered to the surface of the powder particles by dry-mixing them with a high-speed mixer such as a Henschel mixer manufactured by Mitsui Miike Co., Ltd. or a super mixer manufactured by Kawata Manufacturing Co., Ltd.

[0016]

EXAMPLES The present invention will be described below based on examples. <Example 1> Production of powder paint Polyester resin 83.7 parts by weight (Nippon Ester Co., Ltd. product name: ER-6680) Blocked isocyanate 15.3 parts by weight (Daicel Huls product name: BF-1540) Dioxide Titanium 50.0 parts by weight (Ishihara Sangyo's trade name: CR-90) Silane coupling agent 0.50 parts by weight (Toray Dow Corning Silicone's trade name: SH-6062) Leveling agent / acrylic polymer 1.00 parts by weight (BASF Co., Ltd. product name: Acronal 4F) Antifoaming agent / benzoin 0.50 parts by weight (Midori Kagaku Co., Ltd. product name: benzoin) After hot melt kneading with a pressure kneader at 120 ° C, pulverize with a jet mill, and then with a dry airflow classifier, volume 50% diameter becomes 13 μm Thus, the powder particles were classified. To 100 parts by weight of this powder, 0.4 parts by weight of hydrophobic silica fine powder was mixed by stirring with a Henschel mixer to obtain a powder coating material of the present invention.

Example 2 A powder coating material of the present invention was obtained in the same manner as in Example 1 except that the content of the silane coupling agent was 1.00 parts by weight.

Example 3 A powder coating material of the present invention was obtained in the same manner as in Example 1 except that the content of the silane coupling agent was 2.00 parts by weight.

Example 4 A powder coating material of the present invention was obtained in the same manner as in Example 1 except that the content of the silane coupling agent was 2.50 parts by weight.

<Comparative Example 1> The 50% volume diameter after classification was 4.
A powder coating material of Comparative Example 1 was obtained in the same manner as in Example 1 except that the thickness was 5 μm. In this case, much energy was consumed in the crushing process, and the yield was poor.

Comparative Example 2 The 50% volume diameter after classification is 2
Comparative Example 2 The same as Example 1 except that the thickness was 6.0 μm.
A powder coating of

Comparative Example 3 A powder coating material of Comparative Example 3 was obtained in the same manner as in Example 1 except that the silane coupling agent was not used.

Comparative Example 4 Comparative Example 4 was carried out in the same manner as in Example 1 except that 2.00 parts by weight of an epoxy resin (trade name: Epotote YD-014 manufactured by Tohto Kasei Co., Ltd.) was blended in place of the silane coupling agent. A powder coating of

<Example 1> to <Example 4>, <Comparative Example 1>
> To <Comparative Example 4> is applied to a spray gun of a tripo-charging system, and a zinc phosphate-treated steel plate (SPCC-SB plate) having a bright finish has a film thickness of 30 μ after baking.
After spraying so as to obtain m, baking was performed at 200 ° C. As a result, in Comparative Example 1, lumpiness was generated due to the aggregated powder, and unevenness was also recognized on the coated surface. Moreover, in Comparative Example 2, coarse particles were generated and the coating film was poor in smoothness.

The coating film was in good condition <Example 1> to <
Example 4> and <Comparative Example 3> to <Comparative Example 4> were subjected to an accelerated weathering test, a salt spray test (based on JISK5400), and an adhesion test. JIS adhesion test
According to the cross-cut tape method according to K5400, the powder coating material was baked on a steel plate not subjected to surface treatment with a film thickness of 30 μm, immersed in boiling water for 8 hours, and then evaluated by a cross-cut test. Table 1 shows the test results. In Table 1, ∘ ... Good, Δ ... Slightly bad, × ... Poor, XX Very bad. The accelerated weather resistance test (gloss retention:%) was 5
In the case of 00 hr, there is no practical problem if it is 80% or more. 3 in case of 500hr in salt spray test (maximum peeling width: mm)
If it is less than mm, there is no practical problem. Also, the adhesion test is 1
The number of crosses remaining without breaking after peeling the tape in the 00 crosses is shown.

[0026]

[Table 1]

As is clear from Table 1, according to the powder coating material of the present invention, it is possible to obtain a powder coating material which is excellent in weather resistance and rust prevention even when a thin film of 30 μm is formed. it can.

[0028]

As described above, in the present invention, since the average particle diameter of the powder coating material is 5 to 20 μm, the coating film can be made thin, and the silane coupling agent is contained.
It is possible to provide a powder coating which has improved adhesion to an object to be coated and can obtain excellent rustproofness without deteriorating weather resistance.

Claims (2)

[Claims] 1. A powder coating material containing a resin component comprising at least a binder resin and a curing agent, and having a volume average particle diameter of 5 to 20 μm, characterized by containing a silane coupling agent. Body paint. 2. The content of the silane coupling agent in the powder coating material is 0.5 to 2.5 with respect to 100 parts by weight of the resin component.
The powder coating material according to claim 1, which is parts by weight.